Tunnel kiln for heat treatment of cylindrical products

ABSTRACT

Tunnel kiln for heat treatment in a controlled atmosphere with recirculating of gas for cylindrical products, arranged inside support-tubes which move forward in the kiln perpendicularly to their longitudinal axis and wherein the sucking of the gases in the atmosphere of the kiln by several openings on the longitudinal side of the latter and for discharging these gases on the opposite longitudinal side by several openings 15.

"United States Patent 11 1 Weber [4 1 Sept. 16, 1975 TUNNEL KILN FOR HEAT TREATNIENT OF CYLINDRICAL PRODUCTS [75] Inventor:

[73] Assignee: Ceraver, Paris, France [22] Filed: May 3, 1974 21 Appl. No.: 466,661

Jean Weber, Tarbes, France [30] Foreign Application Priority Data 7 May 8, 1973 France 73.16588 [52] US. Cl 432/144; 432/145 [51] Int. Cl. F27B 9/00 [58] Field of Search 432/121, 122, 137, 138,

[56] References Cited UNITED STATES PATENTS 489.017 Koch 432/122 Redmond 432/122 Wemicke 432/122 Primary Examiner-John J. Camby Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT Tunnel kiln for heat treatment in a controlled atmosphere with recirculating of gas for cylindrical products, arranged inside support-tubes which move forward in the kiln perpendicularly to their longitudinal axis and wherein the sucking of the gases in the atmosphere of the kiln by several openings on the longitudinal side of the latter and for discharging these gases on the opposite longitudinal side by several openings 15.

5 Claims, 9 Drawing Figures PATENTED 3,905,759

SHEET 1 UP 4 FIG.1

g TEU SEP 1 51975 SHEET U 4 TUNNEL KILN FOR HEAT TREATMENT OF CYLINDRICAL PRODUCTS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention concerns a tunnel kiln for heat treatment in a controlledatmosphere with recirculating of gas, for cylindrical products arranged inside support tubes comprising means for moving forward the support tubes in the kiln perpendicularly to their longitudinal axis. It applies more particularly to kilns for heat treatment of elongated cylindrical parts such as bars, tubes, etc., more particularly made of a ceramic substance, arranged in tubular supports inside which they roll during their pass through the kiln, in order to avoid any deformation due to their weight or to nonhomogenous heating effects, more particularly to the tunnel kiln which is subject matter of United States patent application Ser. No. 464,091, filed Apr. 25, 1974 for: A tunnel kiln for heat treatment of products having a circular cross-section.

2. Description of the Prior Art Due to the arrangements of the products in tubes arranged in horizontal layers, or in drums, the gaseous exchanges with the atmosphere in the kiln of the products arranged in tubular supports may be hindered, the circulating gases being liable to follow perferentially paths outside the tubular supports, therefore along which they do not pass in contact with the products. This may make the heat treatment incomplete.

It is an object of the present invention to overcome the above disadvantages and to provide a good contact of the circulating gases in the atmosphere of the kiln with the products subjected to heat treatment, establishing a forced gas flow of the atmosphere of the kiln transversally to the axis of the kiln and passing preferentially inside the support tubes.

SUMMARY OF THE INVENTION The tunnel kiln according to the invention is characterized in that it comprises, moreover, means for sucking the gases from the atmosphere of the kiln by several openings on a longitudinal side of the latter and for dis charging the said gases into the kiln on the opposite longitudinal side thereof by several openings so as to make them flow in a preferential way in the support tubes.

It comprises, moreover, preferably at least one of the following characteristics:

The means for discharging the gases of the atmosphere of the kiln into the latter comprise at least a longitudinal lateral chamber parallel to the axis of the kiln and a partition separating that chamber from the kiln, drilled with openings at the level of the cylindrical products subjected to the heat treatment.

The partition separating the chamber from the furnace comprises several contiguous mobile elements perpendicular to the hearth of the kiln and parallel to its axis, resting, by a support, in a longitudinal groove in the hearth, drilled with openings at the level of and opposite the cylindrical products and provided with means for driving support tubes for the products;

In a kiln in which the cylindrical products are arranged in tubes rolling on the hearth of the kiln or in drums, the discharging means for the gases of the atmosphere of the kiln into the latter comprise a series of contiguous distance pieces or spacer assemblies borne by the tubes or arranged between the axles of the drums, spaced apart from the lateral walls of the kiln and provided with openings for the circulating of gases.

It is provided with means for separating, from the gases, the condensable vapours, comprising cooled removable hollow part, this enabling the heat treatment of products giving off condensable vapours, without using an excessively heat-insulating means for the circuit through which the gases in the atmosphere of the kiln flow and without periodic stoppages for the cleaning of that circuit. The chamber is preferably connected to a circuit swept by an inert gas.

The following text describes, by way of an example and with reference to the accompanying drawing, gas flow devices for a tunnel kiln having a controlled atmosphere, according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic section of a gase flow device making the gaseous exchanges between the atmosphere of the kiln and the products to be treated easier.

FIGS. 2 and 3 are a front view and a profile view of an element forming a spacer arrow by constituting the mobile wall of a chamber for the gas flow.

FIG. 4 is an end view of element forming a spacer assembly constituting, by juxtaposition with contiguous elements a mobile wall of a chamber for the circulating of gas, in a kiln in which the products are arranged in support tubes rolling on the hearth.

FIGS. 5 to 8 show elevation views and plane views of the elements forming a distance-piece constituting, by juxtaposition with contiguous elements, a mobile wall of a chamber for the circulating of gas, ina kiln in which the products are arranged in support tubes grouped in drums.

FIG. 9 is a partial end view of a device for purifying gases of the atmosphere of the kiln which are circulating.

DESCRIPTION OF PREFERRED EMBODIMENTS In the gas circulating device in FIG. 1, a flow of gases is caused inside the support tubes 1, 2, arranged in two layers on the hearth 3 of the kiln, the tubes of the lower layer being separated from one another by distancepieces or spacer assemblies 4 sliding in grooves of the hearth. For that purpose, suction is effected in a duct 10 by a fan 11 and discharge is effected by a duct 12, on the recirculated gases in a zone of the kiln into a longitudinal lateral chamber 13. That chamber is limited on one side by a wall 14 provided with a series of elongated slots 15, situated in a plane, parallel to the hearth, extending through the support tubes of each layer.

The chamber 13 may be formed by a continuous series of elements 20 also fulfilling the function of a dis tance-piece or spacer assembly (FIGS. 2 and 3) instead of by a fixed wall such as that in FIG. 1. These elements comprise a stand 21 on which is arranged a hub 22 drilled with elongated holes 15, situated in the diametrical plane of the support tubes of each layer and provided with a rib 23 fonning a cleat. These elements move in a groove 25 formed in the hearth 3.

In the same way, it is possible to modify the distancepieces of the type described in the US. patent application, to make them fulfill the function of a mobile wall.

Thus, FIG. 4 shows a distance-piece or spacer assembly 30, provided with a recess 31, arranged on two tubes 1 of a lower layer and a tube 2 of an upper layer and providing a lateral opening 32 for the passing of the circulating gases. j j

FIGS. '5 and; 6 show a distance-piece or spacer assembly arrangedbetween the axles 51 of the roller sprocketsSZ on the ramp 53 of two adjacent drums 54. In that case, the distance piece 55 drilled with a great number of openings 56 adjacent to the drums, is provided with a hole 57 in which the axles 58 providedwith roller sprockets 59 rotate.

FIGS. 7 and 8 show a distance-piece or spacer assembly arranged between, the axles 61 of the roller sprockets 62 on the ramp 63 of two adjacent drums 64. In that case, the perforated distance-piece 65, drilled with openings 66 .opposite the drums, is fixed to the flange 28 assembled on the sprockets -67, 68 and supporting the intermediate sprockets 69, 70, 71.

When a kilnaccording to the invention has to operate in a definite atmosphere, for example, a reducing or inert atmosphere, one may have to recirculate the gases in one or several zones of the kiln (FIG. 9 The gases become progressively charged with condensable vapors which must be removed before they are deposited on the cold parts of the ducts, thereby possibly obstructing them. For that purpose, a hollow cylindrical part 81 cooled by a water flow, is installed inside the extraction duct 80, in a somewhere the temperature nonnally pre ventsany condensation. The circulating of the gases is provided by the ventilator 82 and the duct 83 leading to the oppositelateral wall to that containing the extraction duct. When the part 81 is charged' with condensate, it is removed into a chamber 84 by means of a rod 85 passing through a packing gland 86, making it pass" rapidly through a fluid-tight valve 87. An inert gas sweeps through the chamber, in the case of the part 81. It is then filled with air, once the part has cooled down, then opened. The part 81 may be removed and replaced by the reverse manoeuvre. A cooling device 88 and a filter 89 may, moreover, be inserted in the gas circuiL. 1

Although the embodiments of the tunnel kiln which have just been described appear perferable, it will be understood that various modifications may be made thereto without going beyond the scope of the invention, it being possible to replace certain elements of the kiln by others which would fulfill the same or a like technical function therein. A

1 claim:

1. ln'a tunnel kiln having an elongated tunnel for heat treatment in a controlled atmosphere with recirculation of gases, of cylindrical products, arranged inside support-tubes and supported thereby, including I means for moving the support tubes in the kiln tunnel perpendicular to their longitudinal axis and along a longitudinal path through said elongated tunnel, the improvement comprising: lateral ducts opening up to respective sides of said tunnel and connected by a gas recirculation duct, means within one of said ducts for sucking gas from one side of said tunnel and discharging gas into said tunnel from the other side thereof, and at least one upright wall member within said tunnel and adjacent the lateral duct discharging re-circulated gas into said kiln with said upright wall member having slots therein at positions corresponding to said tube interiors for causing said re-circulatedgas to flow longitudinally through said tubes and laterally through said kiln as said tubes move longitudinally along a path through said elongated tunnel.

2. Thetunnel kiln according to claim 1, wherein: a longitudinal lateral chamber extendingparallel tothe axis of the kiln is adjacent the duct discharging the gases into the kiln tunnel, and said wall member comprises partition means separating that chamber from the kiln, with said partition means drilled with openings at the level of the cylindrical products carried by said tube and being subjected to the heat treatment.

3.The tunnel kiln according to claim 2,. wherein: the partition means separating the chamber from the kiln comprises several contiguous mobile elements extending perpendicular to the hearth of the kiln and parallel to its axis, resting, by a support, in a longitudinal groove in the hearth, said elementsbeing drilled with openings, at the level of and opposite to the cylindrical: products and provided with means for driving the support tubes for the products. e l

4. The tunnel kiln according to claim 1, wherein: the cylindrical products are arranged in tubes rolling on the hearth of the kiln and the means for discharging the gases of the atmosphere of the kiln into the latter comprise a series of contiguous spacer assemblies borne by the tubes, spaced apart from the lateral walls of the kiln and provided with openings for the circulating of gases.

5. The tunnel kiln according to claim 1 further comprising means for separating, from the gases, the condensable vapors, said separating means comprising a cooled removable hollow part and means for extracting said part through a fluid-tight valve in a chamber. 

1. In a tunnel kiln having an elongated tunnel for heat treatment in a controlled atmosphere with re-circulation of gases, of cylindrical products, arranged inside support-tubes and supported thereby, including means for moving the support tubes in the kiln tunnel perpendicular to their longitudinal axis and along a longitudinal path through said elongated tunnel, the improvement comprising: lateral ducts opening up to respective sides of said tunnel and connected by a gas re-circulation duct, means within one of said ducts for sucking gas from one side of said tunnel and discharging gas into said tunnel from the other side thereof, and at least one upright wall member within said tunnel and adjacent the lateral duct discharging re-circulated gas into said kiln with said upright wall member having slots therein at positions corresponding to said tube interiors for causing said re-circulated gas to flow longitudinally through said tubes and laterally through said kiln as said tubes move longitudinally along a path through said elongated tunnel.
 2. The tunnel kiln according to claim 1, wherein: a longitudinal lateral chamber extending parallel to the axis of the kiln is adjacent the duct discharging the gases into the kiln tunnel, and said wall member comprises partition means separating that chamber from the kiln, with said partition means drilled with openings at the level of the cylindrical products carried by said tube and being subjected to the heat treatment.
 3. The tunnel kiln according to claim 2, wherein: the partition means separating the chamber from the kiln comprises several contiguous mobile elements extending perpendicular to the hearth of the kiln and parallel to its axis, resting, by a support, in a longitudinal groove in the hearth, said elements being drilled with openings, at the level of and opposite to the cylindrical products and provided with means for driving the support tubes for the products.
 4. The tunnel kiln according to claim 1, wherein: the cylindrical products are arranged in tubes rolling on the hearth of the kiln and the means for discharging tHe gases of the atmosphere of the kiln into the latter comprise a series of contiguous spacer assemblies borne by the tubes, spaced apart from the lateral walls of the kiln and provided with openings for the circulating of gases.
 5. The tunnel kiln according to claim 1 further comprising means for separating, from the gases, the condensable vapors, said separating means comprising a cooled removable hollow part and means for extracting said part through a fluid-tight valve in a chamber. 